Astrophysics: Universe's earliest molecular bond found in space

Nature

April 18, 2019

The helium hydride ion HeH+, which has been predicted to be the first molecular ion formed in the Universe, has been detected in space for the first time, reports a paper published in Nature. These findings bring a decades-long search to an end.

The helium hydride ion, created from a helium atom and a proton, was the first type of molecular bond to form in the early stages of the Universe. Over time, it was destroyed to form hydrogen molecules and helium atoms. Although its existence was first demonstrated in the laboratory in 1925, the ion had never been detected in space.

Previous attempts to detect the helium hydride ion in space were limited by the limited resolving power of existing spectrometers at the appropriate wavelengths. However, the high-resolution GREAT spectrometer aboard SOFIA (the Stratospheric Observatory for Infrared Astronomy) has the ability to detect the infrared lines that the helium hydride ion would emit. Using data obtained during three flights of SOFIA in May 2016, Rolf Gusten and colleagues have detected the helium hydride ion in the planetary nebula NGC 7027. The young age of this nebula made it a good candidate for the formation of the helium hydride ion because the conditions are similar to those in the early Universe.